Hammer for impact crushers



uly 39, W460 a... s. EHMANN- 2,404,775

HAMMER FOR IMPACT GRUSHERS Filed Dec. 9, 1941 3 Sheets-Sheet 1 INV'EATTORNEY.

" LESLIE a. EHMAILVN July 3G,, 1% 1.. G. EHMANN HAMMER FOR IMPACTCRUSHERS Filed Dec. 9, 1941 3 Sheets-Sheet 2 ATTORNEY i L. G, ETH-MANN 49 7 5mm FOR IMPACT ciwsnmns Filed 1 9, 1941. s Sheds-Sheet s ATTORNEYPatented July 30, 1946 Leslie G. Elimann,

Portland, 0reg., assignor to Electric Steel Foundry Company, Portland,

0reg., a corporation of Oregon Application December 9, 1941, Serial No.422,205

12 Claims.

The present invention relate to rotary impact crushers or reducers, andmore particularly to a new and improved hammer for use therein.

Rotary impact crushers usually comprise a driven shaft having aplurality of discs arranged thereon with one or more hammers pivotallyattached to the periphery of each disc. The rotor element is mountedwithin a casing including a plurality of cylindrically arranged breakerbars, and is driven at high speed so that material fed thereto iscrushed or pulverized between the hammers and the casing. The hammersusually are of a one piece construction and, depending upon the size andcapacity of the crusher, are of relatively massive proportions. Wearoccurs at the outer edges of the hammer heads, and after a certainperiod of use the amount of wear becomes such that the hammer must bereplaced. Since only about fifteen to twenty percent of the total massof one piece hammers away by use at the time the hammer is replaced, arelatively high proportion of the metal comprising the hammer isscrapped. Crusher hammers, particularly of the type used for reducingore, cement and the like, are made of a very T tough and hardened steelwhich in itself is very expensive, and the loss of so great a proportionof the metal occasioned by the replacement of the entire hammer becomesan item of major expense in the maintenance of a hammer mill.

It has been proposed to use hammers having renewable heads or wearingportions which alone would need replacement after having become worn toan ineflicient condition. Such hammers as have been devised heretoforehave had renewable heads attached to the shank portion by means ofbolts, rivets, or similar means. These require the expenditure of aconsiderable time to loosen and replace, necessitating a costlycessation of operation of the mill because of time involved in reversingor renewing the hammer heads. Moreover, because of the extremeconditions of vibration and other forces attendant upon the operation ofcrushers, such fastening means have become loosened failed, permittingthe release of the hammer and causing considerable damage to the crusherbefore it can be brought to a standstill. A renewable head hammer forcrushers which will withstand severe service and be incapable of flyingapart when in operation has been greatly needed in the art.

It is, therefore, an object of the present invention to provide a newand improved hammer for rotary impact crushers and the like having hasbeen worn or otherwise have 2 a renewable head so attached to the shankthat it cannot separate therefrom during operation of the crusher.

A further object of the invention resides in the provision of a new andimproved impact hammer havinga renewable head wearing portion which issecured to the hammer shank without the use of separate attaching means.

It is a still further object of the invention to provide a novel impacthammer of the character described which is simple and sturdy inconstruction, which is long lived and economical i use, and in which thehead is so attached to the shank that it may be renewed or reversed witha relatively small expenditure of time.

In accordance with an illustrated embodiment of the invention, a crusherimpact hammer is provided comprising a hammer head having a socketformedin one surfacethereofincluding integral portions forming overhangingshoulders. The head is attached to a shank comprising a pair of armshaving a first pair of ends cooperatively arranged in the socket, thearm ends having opposed lateral projections extending cooperativelybeneath corresponding shoulders. The arm are so shaped that they mayreadily be assembled into the head without the need of special tools orfastening means, and so that when the outer ends of the arms are mountedon the crusher rotor discs, separation of the head from the arms ispositively precluded.

Further objects and advantages of the invention will become apparent asthe description proceeds, while the features of novelty characterizingthe invention will be pointed out with greater particularity in theappended claims.

In the drawings, Figure l is a fragmentary longitudinal sectional viewof a portion of a crusher illustrating the arrangement of a plurality ofhammers therein constructed in accordance with one form of the presentinvention; Figure 2 is a cross sectional view through the structureillustrated in Figure 1, taken along the line 22; Figure 3 is anexploded view in perspective of an impact crusher hammer of the typeshown in Figures 1 and 2; Figure 4 i an end view of the hammer shown inFigure 3; Figure 5 is a longitudinal view, partly in cross section, ofthe hammer assembly shown in Figures 3 and 4; Figure 6 is an explodedview in perspective of a hammer constructed in accordance with amodification of the invention; Figure '7 is an end View of the assembledhammer of the modification shown in Figure 6; Figure 8 is a verticalcross sectional view. of the hammer, taken along the line 8-8 of Figure7; Figure 9 is a cross sectional View taken along the line 9+9 of Figure7; Figure 10 is an end view of a hammer constructed in accordance with afurther modification of the invention; Figure 11 is an exploded view inperspective of the hammer head and a fragmentary portion of the shankarms of the modification shown in.'Figure 10; and Figures 12 and 13 areend views of structures similar to those illustrated in Figures 4 and 7,respectively, showing the invention as embodied in knives for shreddingensilage, sugar cane, pineapple and'o-ther similar fibrous materials.

Impact hammers embodying the present invention are adapted for use invarious types and kind of crushers or reducers, and for purposes ofillustration one form of hammer of the present invention is shown inconnection with a crusher of conventional design in the fragmentaryviews of Figures 1 and 2. The crusher comprises a casing including aplurality of axially extending and cylindrically'arranged bars ll.Extending axially through the casing is a shaft !2 having a plurality ofdiscs 13 mounted thereon and keyed thereto in a spaced apart relation.Pivotally attached to the periphery of the discs it are a plurality ofhammers H comprising, shanks l4 having. ey s for cooperativelyreceiving.a through rod idpivotally securing the hammers to the discs l3; andhaving heads 18 which, in the extended position of the hammerarevolveclosely adjacent the bars H of the casing. It will be understood that inoperationthe"rotohfinoluding the discs 13 and hammers H, i revolved. atvery high speeds and hence is subjectedto heavy centrifugal forces, andthat the leading edges of the hammers are subject to considerable wearunder impact with .the material beingcrushed. I

The primary feature of the present invention resides in the provision ofan impact hammer H orsimilar implement in which'the head portion 18 isrenewable, and which is removably attached to the shankportion It insuch manner that misalignment ofthe. arms comprising the shank is allthat is required to remove it therefrom. During the operation of thecrusher misalignment of the shank arms, and consequent removal of thehead therefrom, is precluded, An important advantag o-fthe inventionresides in the fact that the head l3 may be reversed or renewed withinaminimum of time. T v

Referring to Figures 3 to 5, inclusive, each hammer H comprises areversible and renewable tip or head portion {Shaving a socket formed bya longitudinal recess W in the inner surface thereof and extendinglongitudinally of the hammer hea/d. Portions 22 and 23 integral with thehammer head t8 extend over the opposite ends of the recess 2} formingrelatively rugged overhanging shoulders. The hammer shank comprises twopieces, namely, a pair of arms 26 and 25 which have afirst or outer pairof ends having opposed lateral projections 26 and 27 of a cross sectioncorresponding generally to that of the" recess ii in head 13. I The arms2d and 25 are separately insertable into the recess 2!, arm 24 beingadapted for insertion-first, after which it is moved furthermost to theright, as viewed in Figure 5, with theprojectioh 25 extendingcooperatively under the shoulder 23. The surface 2 9 of the arm 2opposite the projection 25 is concavely curved, and the adjacent surface39 of the arm 25 i convex l y curved, the two curvatures being similarso thatin the assembled po- 'sition of the arms they abut against eachother.

4 The center of the curve it is at some point 32 in the shoulder portion22, so that the projection 27 of arm 25 may beinserted into the left ofthe recess ill by rotating the end of arm 25 about the shoulder 22 asindicated by dotted lines 33 in Figure 5.

The innermost ends of the arm 24 and 25 are provided with eye openings34 and 35, respectively, for cooperatively receiving a through rod suchas I5 for securing a plurality of similar hammers to the rotor discs iiiof the crusher. With the arms thus retained in a predetermined alignedrelation of the eyes 34 and 35, withdrawal of the hook ends of the armsfrom the hammer head is positively precluded.

It is preferred to tie the inner end of the arms together to facilitatethe assembly of the hammers in the crusher. Thi tying means comprises akeeper 3? inserted through the eyes 34 and 3.5 and dropped downwardlyinto cooperating slots 38 and in the arms 2 and Z5, respectively. Theopposite. ends of the keeper 3? are provided with heads i2 and 53 whichfit cooperatively into recesses provided therefor in the outer surfacesof the arms about the ends of the slots 38 and 352. The upper surface ofthe keeper 3? is concavely curved so as to conform generally with thecurvature of the eyes 34 and 35. It will be understood, however, thatlittle or no wear will occur'on the. surface of the keeper by virtue ofthe fact that due to centrifugal force the weight of the hammer will beborne entirely by the surface of the eyes opposite the keeper 3?. Inorder to facilitate removal of the keeper 3'! from the slot 33 and 353,additional recesses 4d are provided in the outer surfaces of the arms 24and 25 for the insertion of a punch into an engaging relation with thelowermost edge of the keeper heads.

In the assembled condition of the hammer the shank arms extendgenerallyparallel with respect to each other and in which relation theyare secured when mounted upon the rotor discs by means of the throughrod l5 extending through the eyes in the inner ends of the shank arms.In the operation of the crusher, the hammers will e maintained in aradially extended position with respect to the periphery of the discs,due to the centrifugal force acting outwardly on the hammers. Dependingupon such factors as the length and weight of the hammer, the diameterof the rotor discs, and the speed of rotation of the rotor, thecentrifugal force acting on the hammers will be relatively great, asidefrom the tangential forces resulting from the impact of the hammers withthe material being crushed. The anchorage between the shank and the headis made rugged and sufIicient-ly strong so as to be able to withstandanysuch forces as may be imposed upon the unit. Thus the bridgingshoulders 22 and 23 over the opposite end of the head recess 2i and thelateral projections 28 and 21 hooking underneath such shoulder portionsaremade as heavy as may be required.

The centrifugal force acting upon the hammer head 18 will normally besuch as to prevent a rocking movement thereof on the ends of the shankarms even under the force of impact upon material being crushed. But inorder further to preclude the occurrence of any such rocking movement,the cross section of the recess 2! in the hammer head, and of the endsof'the shank arrns'jfitting cooperatively therein, is generallyelliptical injshane the long axis extending in thelongitudirial'direction of the hammer, as

viewed, for example, in Figure 4. It will furthermore be observed thatthis cross section is somewhat wider at the top than at the bottom, andwith particular respect to the shank arms the corner between theprojections and the adjoining right angular portion of the shank arms isrounded so as to provide greater strength in the region of the corneragainst the tension forces concentrated at this point. The oppositesides of the shank arm 24 and 25 are further provided with shoulders 45and 41 which, in the assembled relation of the hammer, engage againstthe upper edges of the side walls of recess 2| further to precluderelative sidewise movement of the head on the ends of the shank arms.

Referring again to Figure 1, it will be observed that the distancebetween the opposite sides of the pair of shank arms of each hammer isjust somewhat less than the axial spacing between a pair of adjacentrotor discs l3 in order to provide for free pivotal movement of thehammers therebetween. It will also be observed that the width of thehammer heads [8 is somewhat less than the center plane distance betweenadjacent discs l3, but greater than the distance between adjacentsurfaces of a pair of adjacent rotor discs so as to prevent thehammersfrom being pivotally movable into the space between the discs.

The hammer of the modification illustrated in Figures 1 to 5, inclusive,is designed for mounting in a crusher in such manner that the wide, fiatside of the hammer is presented for impacting against the material beingcrushed. In a further modification of the invention, illustrated inFigures 6 to 9, inclusive, a hammer is shown which is adapted formounting in a crusher in such manner that the relatively narrow end ofthe hammer head is presented to the work.

Referring now to Figures 6 to 9, inclusive, the hammer of thismodification comprises a head 5| and a two piece shank formed by arms 52and 53. The inner surface of the hammer head 5| is provided with asocket in the form of an elongated recess 54 having shoulders 55 and 55integral with the head and overhanging the opposite ends of recess 54. Aweb 51 extending lengthwise of the recess 54 and perpendicularly fromthe base thereof divides the recess 54 substantially centrally. The web5! is integral with the head at the base of the recess 54, and with theopposite shoulders 55 and 56.

The shank arms 52 and 53 have a first pair of ends adapted for fittingcooperatively into the recess 54 in the head 5|, having lateralprojections 59 and El, respectively, for fitting snugly under theoverhanging shoulders 55 and 56. The endsof the shank arms are slottedas indicated at 62 and 63, respectively, over the web 51.

The shank arm ends fitting into the socket in head 5| may be ofsubstantially the same width as that of the head. The inner, widened endportions of the shank arms are of a reduced thickness and are so shapedthat in the assembled relation they fit cooperatively together in anoverlapping relation as illustrated more clearly in Figures 7 and 8. Theopposed edges of the for fitting cooperatively shank arms 52 and 53 areprovided with tapered laterally extending flange portions as indicatedat and 65, respectively, which strengthen the tip portions of the shankarms.

In assembling the hammer, the shank arm 53 is inserted first into therecess '54 in the head 5| and moved furthermost to the right, as viewedin Figure 7, so that the lateral projection GI engages under thecooperating overhanging shoulder 56. The surface of the shank arm endopposite the lateral projection 6| is concavely curved as indicated at68, while the adjacent surface 69 of the end shank arm 52 is convexlycurved to permit assembly of the last mentioned arm in a manner similarto that described in connection with the hammer H of the firstmodification. Holding the shank arm 52 in the angular relation indicatedby dotted lines II, the tip 59, is inserted into the space between theshoulder 55 and the arm 53 and, by rotating the shank arm 52 in theclockwise direction, as viewed in Figure '7, into a parallel overlappingrelation with respect to the first arm 53, the projection 59. will moveunder the overhanging shoulder 55, while the adjacent curved surfaces 68and 59 of the shank arm ends fit snugly against each other.

The widened inner ends of the shank arms 52 and 53 are provided witheyes 12 and i3, respectively, which in the assembled relation of theshank arms align with each other forcooperatively receiving a throughrod or bolt corresponding with the rod l5, described in connection withthe hammer of the first modification, for mounting the hammer on theperiphery of the crusher rotor discs. The inner ends of the shank armsbeing thus secured in a predetermined aligned parallel relation, thehead 5| is fixedly secured on the opposite ends of the shank arms. Byvirtue of the web 5'! provided in the head recess 54 which is straddledby the corresponding ends of the shank arms, lateral movement of thehead with respect to the shank arm ends is positively precluded. o Manyother modifications of the invention will readily occur to those skilledin the art. For example, it will be obvious that it is not essential tothe practice of the present invention that the ends of the shank armsfitted into the socket in the hammer head be cooperatively convexly andconcavely curved, asshown in the first two modifications. If desired,the hammer may be constructed as illustrated in Figure 10 which is aslight alteration of the design of the second described modification.The hammer of this modification comprises a head 8| and a pair ofsimilar shank arms 82 and 83. The hammer head 8| is similar to thehammer head 5| except that extending centrally upwardly from the base ofthe recess 84 and at right angles with respect to the web 8! is atransverse ridge 88 having oppositely curved sides merging smoothly withthe base of the recess. The shank arms 82 and 83 have a first pair ofends for cooperatively fitting into the recess 84 in the head 3| forsecuring the hammer head thereto. The ends of the shank arms 82 and 83are provided with lateral projections 89 and 9|, respectively, the endsof the shank arms being furthermore provided with slots 92 and 93 forcooperatively straddling the web 81. It will be observed that the twoshank arms 82 and 83 are substantially similar to the one shank arm 52of the previously described modifications. That is, instead of theadjacent surfaces of the shank arm ends arranged within the head recessbeing oppositely curved for cooperatively abutting together, in thisinstance these surfaces are both convexly curved as indicated at 94 and95, respectively, for fitting smoothly against the opposite surfaces ofthe ridge portion 88 extending transversely in the head recess 84. Thusformed, the shank arms are insertable separately into the correspond-inghead sockets by inserting the tips holding'the shankarms at an anglewith "respect thereto, and then pivoting the shank arms upwardly towardeach other to the final vertical position, causing the projections 89and 9I3 to engage underneath the overhanging'shoulders 96 and91,.respectively, of the head.

In'other respects the arms 82 and 83 of this modification are similar tothe .arms 52 and 53 previously described. It will be obvious that the 1hammer shown in Figures 1 to "5,, inclusive; may also be modified in amanner as last described.

It will be obvious that the recess in the hammer head forming a socketor sockets for the ends 'of thesha'nk pieces and defining overhangingshoulders for retaining the enlarged ends of the shank pieces in placemay be of still other configurations than those shown. Considerablevariation also is possible in the design of the shank pieces as well asof the enlarged ends fitting :into the head recess. The presentinvention resides in the provision of a hammer construction having a twopiece shank, at least one of which shank pieces is insertable into asocket provided in the head at an angle with respect'to the finalassembled position and pivotall'y movable therein to the final positionto secure :the head firmly to the :shank. As the shank pieces are.fastenecl'relative to each other in the final "assembled relation bymeans for mounting the hammer on the crusher :rotor, .separation ofithehammer head from the shank is positively precluded. Thus the meansfastening the head to the shank does not :require the use of any beltsor similar devices :likely to work loose during the operation of thecrusher. The head is readily reversible on the shank and, as required,may be replaced when worn with .a minimum expenditure of eifort andtime.

In Figures '12 and :13 are illustrated shredder hammers of the type usedin swing hammer shredders for'reducing chips, bark, cane, paper, and thelike, and in which the hammer head is'provided with knife-like edges forcutting such material. mer IOI having cutting edges I02 providedon itsnarrow end faces. The shank arms I03 and IM may in all respects besimilar to the shank arms 52 and 53 illustrated in Figures 6 to 9,inclusive, and are cooperatively received in a recess I05 in the hammerhead IllI :in the manner 'hereinbefore described. Figure 13 illustratesa shredder hammer having'a head I06 which-is an adaptation of the headl8 shown in Figures 1 to 5, inclusive. The head I06 is mountedon shankarms corresponding to, those shown in Figures 3 and 5, and is providedwith cutting edges IIJI presented to the work in the same manner'as theimpact surfaces :of the head I8.

.Having described the principleof operation of my invention in What isconsidered to be operative embodiments thereof, I desire to have itunderstood that the specific :details describedin connection with thevarious modifications are merely "illustrative and that the inventionmay be carried :out-in other ways.

I claim:

1. 5A1). impact hammer for rotary crushers comprising a hammer head, 'anelongated recess in the upper surface of said head, a pair of ,shouldersoverhanging the opposite ends of said 1recess,.a pair of arms eachhaving an end extending into corresponding ends of said recess, said armends having lateral projections extending cooperatively undercorresponding of Figure 12 illustrates *a shredder ham- 7 saidoverhanging shoulders, said arms being ins sertable separately into saidrecess, a first of said pair of arms having -a concave curved surfaceopposite the lateral projection thereof, the second of said arms havinga convex curved surface.

opposite the lateral projection thereof for abutting cooperativelyagainst the curved surface of said first arm when said two arms areassembled in said recess for preventing disengagement of saidprojections from said shoulders, the curvatures of said convex andconcave curved surfaces being such that-said second of the arms is movedinto assembled relation with the first arm and head from a positionangularly away from said first arm. I g

2. A reducing implement for use in reducing mills comprising, incombination, a suspending shank and a Work performing head replaceablymounted .on said shank, said work performing head having a practicallyelliptical opening extending laterally therethrough and an adjoiningtransverse shank receiving recess, said head also having integralshoulders of substantially arcuate contour in opposed relation atoppositegends of the recess and adjacent said elliptical Op ning, saidsuspending shank including apair of members having complementary shapescomprising oppositely projecting ends adapted to ,fit into said openingand extend practically to the opposite ends thereof when the shank isassembled with the head, one of said members havingon one side aconcavely curved and substantially arcuate surface adapted to fit thesurface ofone of said shoulders and having .on its opposite side asecond concavely curved surface, the otherof said members having on oneside a concavely curved surface adapted to fit against the other of saidshoulders and a substantially concentric convexly curved surface on itsopposite side adapted to fit closely adjacent said secondconcavelycurved surface, said other of the members being insertable intoassembled relation with the head by angular movement about the ,adjacentarcuate shoulder surface, and the .end of said shank practically fillingsaid opening and recess.

3. A reducing implement for use in reducing mills comprising, incombination, ,a suspending shank and a workperforming head replaceablymounted on said shank, said work performing head having an openingextending laterally therethrough and an adjoining transverse shankreceiving recess, said head also having integral shoulders ofsubstantially arcuate contour in opposed relation at opposite ends of.the

recess and adjacent said opening, said suspending shank including a pairof members having complementary shapes comprising oppositely projectingends adapted to fit into said opening and extend practically to theopposite ends thereof when the shank is assembled with the head, one ofsaid members having on one side .a .concavely curved surface adapted tofit adjacent the surface of one of said shoulders and having on itsopposite side ,a second concavely curved surface, the other of saidmembers having on one side a concavely curved surface adapted to fitagainst the other of saidshoulders and a convexly curved surface on itsopposite jacent arcuate shoulder surface.

,4. :Ameducing .implementjfor use in reducing mills comprising, incombination, a suspending shank and a work performing head replaceablymounted on said shank, said work performing head having an openingextending laterally and an adjoining transverse shank receiving recess,said head also having shoulders in opposed relation at opposite endsofthe recess and adjacent said opening, said suspending shank includingapair of members having complementary shapes comprising oppositelyprojecting ends adapted to fit into said opening and extend practicallyto the opposite ends thereof when the shank is assembled with the head,one of said members having on one side a surface adapted to fit adjacentthe surface of one of said shoulders and having on its opposite side aconcavely curved surface, the other of said members having on one side asurface adapted to fit against the other of said shoulders and aconvexly curved surface on its opposite side adapted to fit closelyadjacent said concavely curved surface, said other of the members beinginsertable into assembled relation with the head by angular movementabout the adjacent arcuate shoulder surface, and the end of said shankpractically filling said opening and recess.

5. In a reducing implement for use in reducing mills, the combination ofa suspending shank comprising a pair ofmembers having complementaryshapes and substantially aligned oppositely projecting end portions ofnon-circular section, one of said members having on one side asubstantially arcuate curved surface adjacent the projecting end portionthereof and on its opposite side a concavely curved surface, the otherof said members having a substantially arcuate curved surface adjacentthe projecting end portion thereof and a substantially concentric curvedsurface on the opposite side thereof adapted to fit said concavelycurved surface of the first defined member so that said oppositelyprojecting end portions together form a practically continuous endportion of non-circular section.

6. In a reducing implement for use in reducing mils, the combination ofa suspending shank comprising a pair of members having complementaryshapes and angularly projecting end portions of somewhat ellipticalsection, one of said members having on one side a curved surfaceadjacent the projecting end portion thereof and on its opposite side aconcavely curved surface, the other of said members having asubstantially arcuate curved surface adjacent the projecting end portionthereof and a substantially concentric curved surface on the oppositeside thereof adapted to fit said concavely curved surface of the firstdefined member.

'7. A reducing element for use in a reducing mill or the like andcomprising, in combination, a suspending shank and a work performinghead replaceably mounted on said shank, said shank including a pair ofmembers having complementary shapes, each of said members including ashank arm having at one end an integral foot portion comprising anoutwardly projecting'toe part and an oppositely disposed heel surface,and each of said members having a substantially arcuate surfaceadjoining said shank arm and said outward projecting toe part, one ofsaid members having a concave heel surface, the second of said membershaving a convex heel surface substantially concentric with respect tosaid arcuate surface thereof and adapted to fit snugly adjacent saidconcave surface, and said work 1.0 perform-ing head. comprisingabody-having in one side thereof a recess adaptedto conform to said footportionswhen the heel surfaces thereof are. incontact; said-body, alsohaving; integral shoulders with opposed arcuate, surfacesadapted tooverlie said toe portions, said, workperforming head being, placed in,interlocked relation 'on'said shank by angular swinging movement: ofsaid second of the membersabout thejadjacentflarcuate surface of oneofsaid shoulders to a position .such that said foot portionspractically-fill said I recess andnthe toe portions underliesaidgshoulde'rs. I 111" 8. A re'ducingelement for use in a reducing-millor the like and comprising, incombinationha suspendingyshank and .a"workperforming head replaceably mounted on said shank, said shankincluding a pair of members having complementary shapes, each of saidmembers: including a shank arm having at one end an integral footportion comprising an outwardly projecting toe part and an oppositelydisposed heel surface, and each of said members having a curved surfaceadjoining said shank arm and said outward projecting toe part, one ofsaid members having a concave heel surface, the second of said membershaving a convex heel surface adapted to fit snugly adjacent said concavesurface, and said work performing head comprising a body having in oneside thereof a recess adapted to conform to said foot portions when theheel surfaces thereof are in contact, said body also having integralshoulders with opposed surfaces adapted to overlie said toe portions,said work performing head being laced in interlocked relation on saidshank by angular swinging movement of said second of the members aboutthe adjacent surface of one of said shoulders to a position such thatsaid foot portions practically fill said recess and the toe portionsunderlie said shoulders.

9. A reducing element in accordance with claim 8 wherein said suspendingshank is characterized by having side surfaces of said shank armsadapted to overlap in assembled relation and in a plane substantiallylongitudinal of said foot portion.

10. A reducing element in accordance with claim 9 wherein the recess insaid work performing head is divided by a partitioning wall extendingbetween said shoulders, and the foot portions of said shank arelongitudinally slotted to fit over said partitioning wall.

11. A reducing element for use in a reducing mill or the like andcomprising, in combination, a suspending shank and a work performinghead replaceably mounted on said shank, said shank including a pair ofmembers having complementary shapes including oppositely offset legportions adapted to overlap in assembled relation, each of said membershaving a foot portion at one end including a heel surface and a toe partprojecting outwardly in a sidewise direction with respect to sa d offsetleg portions, each of said members having a curved surface adjoiningsaid projecting toe part, and said foot portions being slotted intermedate the sides and longitudinally thereof, said work performing headcomprising a body having in opposite sides thereof similar recessesseparated by an integral partition, said recesses being of a shapeclosely conforming to said foot portions when the heel surfaces are incontact and said partition extends through the slots in the feet, saidbody also having integral shoulders with opposed curved surfaces adaptedto overlie said toe portions, said work erforming '11 head being placedin interlocked relation on said shank by angular swinging movement of atleast one of said members about the adjacent curved shoulder surface andin a direction such that said oifset leg portions move acrossoverlapping relation.

12; In a reducing implement for use in a re- V ducing mill or the like,the combination'of a replaceable work performing head adapted to becarried in interlocked relation by a suspending shank composed of a pairof" members having longitudinally slotted and oppositely projectingcurved feet swingable into said interlocked relation with the workperforming head about axes substantially perpendicular to saidlongitudinal slot, said work performing head comprising a one anotherinto body having top,

I2 end and side walls, said side walls having oppositely facing recessestherein open at the topand separated by. an integral partition adaptedto fitsaid longitudinal slots, said recesses being shaped to provideshoulders at 0p-' posite ends adjacent the top wall and adapted tooverlie said oppositely projecting feet on opposite sides of saidpartition, the opposed surfaces of said shoulders being substantiallyarcuate, and said recesses also being curved to conform to said feet.in' the assembled relation therewith and to permit swinging movement ofat least one of said feet about the adjacent arcuate shoulder surface toefiect the interlocked assembled relation of said head and shank.

LESLIE G. EHMANN.

Certificate of Correction Patent No. 2,404,775. July so, 1946. LESLIE G.EHMANN It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Column 10, line 48, for the claim reference numeral 9 read 8;and that the said Letters Patent should be read With this correctiontherein that the same may conform to the record of the case in thePatent Ofiice.

Signed and sealed this 29th day of October, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

